Combined grinding and separating apparatus for granular substances



COMBINED GRINDING AND SEPARATING APPARATUS FOR GRANULAR SUBSTANCES Filed Dec. 16, 1933 2 Sheets-Sheet 1 Fig.1.

INYEN TOR.

'ALBIN BERTHOLD HELBIG.

ATTORNEY. (X /hA -V March 24, 1936. A B. HE 'BIG. 2,034,981

COMBINED GRINDING AND SBPARATING APPARATUS FOR GRANULAR SUBSTANCES Filed Dec. 16, 1933 2 Sheets-Sheet 2 \lNvENToR. I

ALBIN Bemuow Hume.

Patented Mar. 24, 1936 columnar) citmnmo AND SEPARATING APPARATUS ron GRANULAR SUBSTANCES Albin BertholdHelbig, Kaiserslautern, Germany, assignor of one-half to VictorBalzar Reichwald, Kent, England Application December 16, 1933, Serial No. 702,799

. In Germany December 22, 1932 4 Claims. (Cl. 209-6) In connection with the grinding of various materials in mills the practice is now largely adopted of. combining the process of grinding with a process of drying the material by-means of hot gas passing through the mill, and efiecting separation of the flour or dust from the grit by means of a pneumatic separator. The usual procedure is as follows:

Hot gas. is passed through the mill at high 10 velocity and carries out of the mill a mixture of grit and fine dust. This mixture is carried by the gas stream'to the pneumatic separator, which separates the dust from the grit, the grit being returned to the mill, and the dust passing to a cyclone dust collector or equivalent apparatus. In this process a very high percentage of power expended is taken by the fan of the pneumatic separator, which propels the stream of gas, the percentage varying according to the fineness of powder required and the grinding quality of the material. With ooal'the percentage may amount to from 30 to 50%, and with materials of higher specific gravity the percentage .nray be' so high as to render the gas-swept mill uneconomical.

According to my invention the power consumption for propelling the gas is greatly reduced by using a mechanical conveyor for taking thewet mill feed, together with the mixture of coarse and fine granules coming from the mill, to the pneumatic separator and using the hot gas for drying the material on its way to the separator and for separating the fine flour from the coarse in the separator, in which the mixture ispro-. jected into the hot gas stream. The velocity which must be imparted to'thegas stream by the fan of the separator in this process, is very much lower than is required in the above mentioned process, wherein the hot gas sweeps 40 through the mill and carries the mill product to the separator. The drying is done on the conveyor, and in the separator, and not in the mill. An embodiment of the invention is shown in the annexed drawings, in which Fig. 1 is a general 415 view of the apparatus, with the conveyor shaft in section, and Fig. 2 is a vertical section of the pneumatic separator, to a larger scale.

Referring first to Fig. l, A represents the grinding mill, B the pneumatic separator, and C the conveyor, which is an endless chain conveyor, with buckets, working in a shaft D. The crude granular mixture is fed into the lower end of the shaft at E. There is also at this part of the.

shaft an inlet G for hot gas, and the mill discharges into the lower end of the shaft at F.

The conveyor carries upwards the fresh material and the mixture of grit and dust received from the mill, and discharges it through a chute H into the pneumatic separator, in which the material is fed onto a rapidly spinning distributing 5 disk-J on a shaft J driven by an electromotor K, so that the grit and dust are flung off the disk by centrifugal force into the hopper L wherein the disk works. This hopper has anoutlet M connected by a pipe N to the feedopening of 10 the mill, and the grit flung off the disk is by this m'eans conveyed to the mill. The hopper outlet M is connected by a pipe 0 to the conveyor shaft D, and above the hopper L, within the casing P of the separator, there is a fan Q driven by 15 an electromotor Q mounted on the casing. This fan Q- sucks the hot gas through the hopper,

past the disk J, so that the stream of gas separates the dust from the mixture flung ofi the disk and carries it upwards. The velocity which 2 must be imparted to the gas stream depends on the required degree of fineness of the finished product. r

The fan iiings the dust laden gas. outwards against a cylindrical partition R in the casing, 25 so that the stream is deflected downwards towards the outlet S for the. finishedproduct and then upwards again towards an annular slot U in an annular partition U of the chamber surrounding the partition R. The dust separated 30 from the gas stream by gravity descends to the outlet S, which is connected by a pipe T to the receptable for the dust.

The annular slot U discharges the waste gas from the separator through'the outlet V near 35 the top of the casing into the atmosphere or in a. dust collector.

v The passage through the slot U is regulatable by an annular valve W operated by means of a screw spindle X and manually actuated nut Y. 40

The hopper L has in its wall an opening a,

' controlled by an annular slide 12, which can be raised and lowered .by' means of a screw spindle c "and a manually actuated nut d for regulating the passage of gas from the casing into the 45 hopper. It will be understood that when this opening a is uncovered the fan sucks into the hopper, outof the surrounding casing, some of the gas which has already passed through the hopper.

If the supply of hot gas through the shaft D of the conveyor is sufllcient to carry the dust out of the hopper into the casing the slide b is fully closed, and there is no returnof gas to the. hopper. The volume of gas varies, however, ac- 55 more or less, and some gas is sucked back into the hopper, the valve W being at the same time so adjusted to restrict the outlet through the slot U which gives passage only to a stream of waste gas carrying away moisture taken from the feed. The separator then works with a volume of gas circulating therein.

For efliciency of operation I design the pneumatic separator so that the cross-section of the gas inlet is equal to the aggregate cross-sections of the gas passages in the separator.

What I claim as my invention and desire to secure by Letters Patent of the United States 1s:

1. In a pneumatic separator for granular materials the combination of a hopper having at the lower part thereof an outlet for grit and a gas inlet separate from said outlet, and having also in its wall an opening for inlet of gas, an adjustable cover regulating the admission of gas to said hopper through said wall opening, a conduit supplying gas to the inlet at the lower part of said hopper, a rotatable distributing disk in said hopper, a mechanical conveyor for feeding granular material into said hopper and on to said disk, a casing surrounding said hopper, having at the upper part thereof an outlet for gas and at the lower part thereof an outlet for dust, a fan in said casing above said hopper,

adapted to suck gas into and through said propelled by said fan is compelled to take a downhopper, and a deflecting wall in said casing, facing the circumference of said fan, whereby gas also in its wall an opening for inlet of gas, an adjustable cover regulating the admission of gas to said hopper through said wall opening, a conduit supplying gas to the inlet at the'lower part of said hopper, a rotatable distributing disk in said hopper, a mechanical conveyor for feeding granular material into said hopper and on to in said casing, around said deflecting wall, having a slot for the passage of gas, and a valve regulating the passage of gas through said slot, for

the purpose set forth. 3. In a pneumatic separator for granular materials the combination of a hopper having an opening in the wall thereof, an adjustable cover controlling said opening, means for supplying gas to said 'hopper at the bottom thereof, a rotatable distributing disk in said hopper, means for feeding granular material into said hopper and onto said disk, a casing enclosing said hopper and having two outlets, one for the discharge of the waste gas at the upper part of the casing and the otherfor the discharge of the fine granular material at the bottom, means for regulating said waste gas outlet, a fan in said casing above said hopper, adapted to suck a stream of gas through said hopper and discharge gas into said casing, and a partition in said casing, facing the rim of said fan and defiecting gas delivered by said fan towards said wall opening of the top of said hopper, for the purpose set forth.

4. In a combined drying, grinding and separating apparatus the combination of agrinding mill, a centrifugal pneumatic separator having at the-bottom a gas inlet, an outlet for coarse granular material and an outlet for fine granularmaterial, and having at the top a feed inlet and a waste gas outlet, said separator comprising a rotary distributor, and a horizontal fan, a mechanical conveyor for feeding the product of said mill together with wet fresh raw material to the feed inlet of said separator, means for feeding the coarse material discharged by said separator to said mill, and means for conducting a stream of hot gas along the path of said conveyor and to the gas inlet of said separator.

- ALBIN BERTHOLD I-IELBIG. 

